Code division multiple access (CDMA) is a technique that allows a communications system to accommodate a large number of system users. CDMA uses a spread spectrum modulation technique, where the signal energy of each channel is spread over a wide frequency band. Multiple channels each correspond to a different system user occupying the same frequency band.
Wideband code-division multiple access (WCDMA) is based on an ITU standard derived from code-division multiple access (CDMA). WCDMA is a third-generation mobile wireless technology. WCDMA can support mobile/portable voice, images, data, and video communications at up to 2 Mbps (local area access) or 384 Kbps (wide area access). Each analog input signal is converted into a digital signal that is spread spectrum coded for transmission over a broad range of frequencies.
User devices negotiate with a base station for a particular bandwidth when the user device is ready to transmit data. The user will be assigned a spreading factor and a code number to differentiate from other users. The spreading factor is associated with allocated bandwidth, and it typically a number that is an integral power of two from 1 to 256. The bandwidth is inversely proportional to the spreading factor. The code number is a number that is less than the spreading factor.
A channelization code is generated in response to the code number and the spreading factor. The data is multiplied by the channelization code after the channelization code is generated. The data is then scrambled. The data is broadcast after the data is scrambled.